Improved characterization of potential aeroallergens is much needed by medical clinicians. Primary aims of the study are to apply modern techniques of air spora study to accomplish the following: 1. To characterize qualitatively the air spora, mainly fungi and pollens, of major regions of Pennsylvania; 2. To provide quantitative volumetric data on air spora; 3. To characterize circadian (daily) and seasonal periodicities of individual kinds of spores. Methods include use of efficient volumetric (Hirst) spore traps, operating 24 hours a day and providing time-related deposits of air spora. Counts and identifications are by microscopic inspection of spores. Traps are situated ca. 100 ft. above ground to assess general air spora concentration in the areas, and are located to provide data representative of three different regions. Weather data are being studied to determine relations of comparative climatology and phenological events and zones of valid application of sampling site data. The present sampling locations in Pennsylvania are in or near State College (University Park), Pittsburgh (Oakland) and Philadelphia (Jenkintown).